Wheel assemblies for use with load bearing platforms

ABSTRACT

A wheel assembly for supporting a load bearing platform includes a primary wheel and at least four secondary wheels that are of equal size. The primary wheel includes at least one planar member having an even number of axles at fixed locations extending perpendicularly therefrom with one secondary wheel mounted on each axle. The fixed locations are angularly equidistant apart and also equidistant from the central axis of the primary wheel. The diameter of each secondary wheel is greater than is the distance between locations, and adjacent secondary wheels are arranged to roll in separate, parallel paths.

This application is a division of pending U.S. patent application Ser.No. 10/647,697 that was filed Aug. 25, 2003, now U.S. Pat. No.7,044,481, which, in turn, is a continuation-in-part of U.S. Pat. No.6,609,719, 2002 which, in turn, is a continuation-in-part of U.S. Pat.No. 6,357,765, filed on Aug. 3, 2000 and issued on Mar. 19, 2002.

TECHNICAL FIELD

This invention relates to wheel assemblies that are used to support loadcarrying platforms with increased safety, particularly when traversingrough surfaces and rolling over small obstacles.

More particularly, this invention relates to wheel assemblies thatprovide load carrying platforms with means to roll across smallobstacles without wheel drag, and to provide braking means for theplatform.

BACKGROUND ART

A large variety of load bearing platforms are used in industry totransport goods from on place to another or to serve as mobileinstrument or tool stations and the like. Such platforms are typicallysupported upon casters or wheel assemblies, either fixed or swiveling,to provide a rolling support for the platforms.

A problem frequently faced in the use of such platforms is the tendencyfor wheels to drag when encountering small obstacles such asconstruction debris, uneven floor or sidewalk joints, and the like. Thatproblem is particularly acute with platforms used in work environmentsin which the platform must cross electrical cords or pneumatic hosesthat power other equipment. Further, cargo carrying platforms aresometimes loaded beyond their safe capacity, thus creating anotherhazardous condition.

There are a number of different wheel assemblies in the prior art thatpropose to address those problems. For example, wheel assemblies thatinclude a primary wheel carrying a plurality of smaller, secondarywheels are shown in U.S. Pat. No. 3,208,544 to Colvin; U.S. Pat. No.1,326,679 to Macbeth et al; U.S. Pat. No. 795,620 to Jones; and U.S.Pat. No. 722,433 to Ritchie. Wheel assemblies employing braking meansused in association with walkers are described in U.S. Pat. No.6,068,273 to Rao et al; in U.S. Pat. No. 5,112,044 to Dubats; and inU.S. Pat. No. 5,020,560 to Turbeville.

The wheel assemblies described in the cited prior art do notsatisfactorily address the needs for wheel assemblies that surmountsmall obstacles without wheel drag, and prevent overloading of a mobileplatform. This invention fills that need.

SUMMARY OF THE INVENTION

Wheel assemblies that are suitable for use to support load bearingplatforms, in a first embodiment, comprise a primary wheel member havingan even number, but at least four, secondary wheels mounted thereon. Allof the secondary wheels are of equal size, are spaced apart a distancethat is less than the secondary wheel diameter, and are fixed at equaldistances from the axles of the primary wheel so that angularly adjacentsecondary wheels overlap but travel in separate and parallel tracks.Brake means that effectively limit the load place upon the wheelassembly comprise a second embodiment of this invention.

Hence, it is an object of this invention to provide a wheel assemblythat rolls over obstacles without wheel drag.

It is another object of this invention to provide a wheel assembly thatprovides a safety braking mechanism that prevents overloading of a cargoplatform, yet is capable of transporting heavy loads.

Other objects and advantages of this invention will become evident froma study of the following description and accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partially broken away side view of a wheel assembly rollingover a surface and showing its operation in traversing an obstacle;

FIG. 2 is a first embodiment of a wheel assembly that allows a loadcarrying platform to roll across a small obstruction without wheel drag;

FIG. 3 is another embodiment of the wheel assembly of FIG. 1;

FIG. 4 is an oblique view of a wheel and brake assembly for a loadcarrying platform;

FIG. 5 is a semi-schematic side view of the wheel and brake assembly ofFIG. 4; and

FIG. 6 is a second oblique, and partially broken away, view of the wheeland brake assembly of FIG. 4.

DESCRIPTION OF THE INVENTION

In a broad sense, applicant's invention comprises wheel assemblies tosupport a load carrying platform and to move that platform from place toplace in a safe and convenient manner. One of those wheel assemblies isarranged to surmount obstacles without wheel drag. That assemblycomprises a primary wheel that is arranged to rotate freely about acentral axis. The primary wheel includes a generally circular planarmember that supports a plurality, at least four, axle members, and eachaxle carries a secondary wheel. Each axle is at a fixed location on, andextends perpendicularly from, the planar member. The axle locations areangularly equidistant apart and also equi-distant from the central axis.

All secondary wheels are of equal diameter and may be configured as agenerally cylindrical disk. The diameter of each secondary wheel isgreater than is the distance between angularly adjacent axles, resultingin overlap of adjacent secondary wheels. The axles and wheels arearranged such that two angularly adjacent wheels are in rolling contactwith a surface at any one time, and each secondary wheel rotatesindependently of any other secondary wheel and of the primary wheel aswell. That arrangement causes one wheel of an angularly adjacent pair toroll upon a surface in a separate and parallel track with the otherwheel of the adjacent pair.

The mode of operation of applicant's obstacle traversing wheel assemblyis illustrated in FIG. 1 that is a view of the assembly rolling acrossan obstruction. Turning now to that Figure, the wheel assembly 10includes at least one primary wheel 14 that is arranged to rotate abouta central axis 75. An even number of secondary wheels 18 arerotationally mounted on corresponding axle means 16 that extendperpendicularly from the primary wheel. At least four secondary wheelsmust be provided for the wheel assembly to function, and an assemblyusing either six or eight secondary wheels is preferred. Wheels 18 arespaced apart a distance that is less than one wheel diameter and arelocated equidistant from each other and from axles 16. As may be seenfrom the drawing, that arrangement causes adjacent secondary wheels tooverlap, and two adjacent secondary wheels, shown as 18 a and 18 b, arein rolling contact with a surface being traversed at any one time.

Wheel assembly 10 is shown rolling along a surface 70 as it bumps intosurface obstruction 72. Obstruction 72 typically might be an electricalcord or pneumatic line lying on a workplace floor, a small stone orbranch on a parking lot or pavement surface, or an irregularity ordepression in a sidewalk or other traversing surface. As assembly 10moves to the right along an unobstructed surface, only the twolowermost, 18 a and 18 b, of the secondary wheels are in rolling contactwith surface 70. The remaining secondary wheels and the primary wheel 14are motionless. As secondary wheel 18 b strikes obstruction 72, itstalls and causes a right-ward tilt of the entire wheel assembly 10,bringing secondary wheel 18c downward to roll over the obstruction. Theforce required to precipitate that rotational tilt is modest, amountingto little more than the force required to lift the wheel assembly (andthe weight that it supports) a short distance. That distance comprises aspan amounting to the difference in distance 77 between the central axis75 of the wheel assembly 10 and surface 70 and the longest distance 79between axis 75 and the circumference of secondary wheel 18 b, incontact with the obstruction 72. Distance 77 may be viewed as being theeffective radius of the wheel assembly, and twice that distance thenconstitutes the effective diameter of the wheel assembly. As may beappreciated, the structure of the wheel assembly allows it to literallywalk over small obstructions, and much of the lifting force required issupplied by the forward momentum of the wheel and its supported weight.

As has been set out before, the wheel assembly of this inventionrequires a minimum of four secondary wheels (and preferably six oreight) that are equi-spaced around the circumference of a primary wheelmeans. Because the diameter of each secondary wheel is greater than isthe distance between wheels, adjacent wheels overlap and must behorizontally offset one from the next. Thus, when the wheel assemblytraverses a surface, the two wheels in contact with that surface followseparate, parallel tracks, one wheel in each track. That geometry,separate and parallel tracking of adjacent wheels, that is pivotallyattached to a load-supporting frame through a conventional yoke or horn.

FIG. 2 illustrates a first detailed embodiment of wheel assembly 10 thatwas described in relation to FIG. 1. This embodiment includes a primarywheel comprising a pair of wheel holders 12 and 14 that are arranged torotate about a central axis 75. The two wheel holders are secured one tothe other in a held apart relationship by way of a cylindrical spacerand bearing member 31 disposed axially between the two wheel holders.Wheels 33 of this embodiment are disk shaped and are mounted on stubaxles 35 that extend inwardly from the wheels holders 12 and 14. Axles35 are secured to the wheel holders as by locking nut 37 or othersuitable means. The axles and wheel holders are arranged so thatadjacent wheels are journeled one from holder 12 and the next fromholder 14. Further, adjacent wheels 33 are located at fixed pointsequidistant one from the other and from the center of spacer member 31at a distance less than the diameter of the wheels, thus causingadjacent wheels to overlap. Bearing member 31 is sized such that the twowheel holders are fixed apart a distance slightly greater than twice thethickness of an individual secondary wheel 33, thereby allowing adjacentwheels to overlap and to also rotate freely.

A second embodiment of the wheel assembly is illustrated in FIG. 3. Thatembodiment employs but a single wheel holder 41 that is provided with acentral bore 43 journaled for rotation about a shaft or axle. An evennumber of stub axles 45, one for each wheel, are fixed to holder 41 andone wheel 33 is mounted on each axle. A spacer means 34, somewhat longerthan the width of a single wheel and preferably cylindrical in form, ismounted next to the holder 41 on alternate axles so as allow adjacentwheels to overlap without interference. Spacer 34 may be formed as aseparate element, or may be formed as an integral boss projecting fromone side of wheel 33. As in the embodiment of FIG. 2, wheels 33 are allthe same diameter and are equi-spaced, one from another, at a distanceless than that of the wheel diameter.

As has been set out before, the wheel assembly of this inventionrequires a minimum of four secondary wheels equi-spaced around thecircumference of a primary wheel means. Because the diameter of eachsecondary wheel is greater than is the distance between wheels, adjacentwheels overlap and are offset one to another. Thus, when the wheelassembly traverses a surface, the two wheels in contact with thatsurface follow separate but parallel tracks, one wheel in each track.That geometry, separate and parallel tracking of adjacent wheels, tendsto increase the stability of a wheel assembly that is pivotally attachedto a load-supporting frame through a conventional yoke or hornarrangement. It can further be appreciated that the overlappingarrangement of adjacent secondary wheels can best be obtained throughuse of an even number of secondary wheels, preferably four, six oreight, and most preferably six or eight.

A different embodiment of this invention is illustrated in FIGS. 4, 5,and 6 provides a wheel and brake assembly 175 that is advantageouslymounted in combination with two or more of the wheel assemblies of FIGS.2 and 3 to support a load carrying platform. Referring specifically toFIGS. 4, 5, and 6, the assembly 175 includes a caster 190 that isrotationally mounted between the arms of yoke 192 by means of axle 193that extends between the yoke arms. Yoke 192 is cantilevered from pivotmember 195 and is arranged so that a downward pressure exerted upon rearlegs 170, 171 upon pivot 195 causes the yoke axle end and caster 190 torise relative to the yoke pivot end.

Yoke 192 terminates at its pivot end in an L-shaped bracket having avertical arm 197 and a horizontal stop member 198. Stop member 198serves to limit the rotational travel of the yoke arms about pivot 195by engagement with the inner side of the assembly housing 200. A springor pneumatic resistance may be contained within cylinder 205. Thatresistance acts through connecting rod 206, vertical arm 197, and yokearms 192 to urge caster 190 downwardly in opposition to the upward forceon the caster that is produced by a load upon the platform that issupported by the wheel assemblies. One or more brake pads 208 aremounted on the underside of assembly housing 200 at a location abovecaster axle 193.

When enough downward force is applied to the load bearing platformsupported by the wheel assemblies, the caster is urged upwardly to thepoint that caster tread 191 contacts and drags against brake pads 208thus inhibiting or stopping rotation of the caster. The magnitude of theforce produced by resistance 205 is preferably adjustable so that it canbe adjusted to the load carrying capacity of the platform. Suchadjustment may be obtained by an appropriate selection of the spring orpneumatic resistance member contained within housing 205, or through athreaded adjustment means 209 that act to change the spring tension orpneumatic resistance. That arrangement prevents a user of the loadcarrying platform from dangerously overloading the platform, and also toapply a brake to the movement of the platform by pressing down on ahandle or frame of the platform.

The wheel assemblies of this invention has been shown and described withrespect to certain embodiments thereof and that description is for thepurpose of illustration and not of limitation. Other variations andmodifications of the described invention will be apparent to thoseskilled in the art and are included within the scope of the invention asset out in the appended claims.

1. A wheel assembly that is arranged to support a load carrying platformand to roll on a surface, comprising: a generally planar primary wheelthat is rotatable about a central axis, said primary wheel comprising asingle planar member, said planar member having a plurality of stubaxles at fixed locations extending perpendicularly outwardly from oneside thereof, said locations being angularly equidistant apart andequidistant as well from the central axis; and an even number ofsecondary wheels, one wheel mounted on each stub axle, said secondarywheels being of equal diameter and configured as a generally cylindricaldisk having a diameter greater than the distance between angularlyadjacent stub axles, said axles and wheels arranged such that at leasttwo angularly adjacent wheels are in rolling contact with said surfaceat any one time, each of said secondary wheels arranged to freely rotateindependently of any other secondary wheel, and independently as well ofsaid primary wheel, said wheels positioned along their respective axlesin a manner causing each wheel of an angularly adjacent pair of wheelsthat is in contact with said surface to roll along a separate andparallel track.
 2. The wheel assembly according to claim 1 wherein thesecondary wheels are of equal width and wherein a spacer means ismounted on alternate stub axles adjacent said planer member, the lengthof said spacer means being greater than is the width of a secondarywheel.
 3. The wheel assembly according to claim 2 wherein said spacermeans comprises a cylindrical element having an axial bore sized to fitover said stub axle, and wherein the height of said cylindrical elementis greater than is the width of a secondary wheel.
 4. The wheel assemblyaccording to claim 2 wherein said spacer means comprises a cylindricalboss projecting axially from one side of the secondary wheel.
 5. Thewheel assembly according to claim 1 having six secondary wheels.
 6. Thewheel assembly according to claim 1 having eight secondary wheels.
 7. Awheel assembly that is arranged to support a load carrying platform andto roll on a surface, comprising: a generally planar primary wheel thatis rotatable about a central axis, said primary wheel comprising asingle planar member, said planar member having four stub axles at fixedlocations extending perpendicularly outwardly from one side thereof,said locations being angularly equidistant apart and equidistant as wellfrom the central axis; four secondary wheels, one wheel mounted on eachstub axle, said secondary wheels being of equal width and diameter andconfigured as a generally cylindrical disk having a diameter greaterthan the distance between angularly adjacent stub axles; and two spacermeans mounted on alternate stub axles adjacent said planar member, thelength of said spacer means being greater than is the width of asecondary wheel, said axles and wheels arranged such that at least twoangularly adjacent wheels are in rolling contact with said surface atany one time, each of said secondary wheels arranged to freely rotateindependently of any other secondary wheel, and independently as well ofsaid primary wheel, said wheels positioned along their respective axlesin a manner causing each wheel of an angularly adjacent pair of wheelsthat is in contact with said surface to roll along a separate andparallel track.
 8. The wheel assembly according to claim 7 wherein saidspacer means comprises a cylindrical element having an axial bore sizedto fit over said stub axle, and wherein the height of said cylindricalelement is greater than is the width of a secondary wheel.
 9. The wheelassembly according to claim 7 wherein said spacer means comprises acylindrical boss projecting axially from one side of the secondarywheel.
 10. A wheel assembly that is arranged to support a load carryingplatform and to roll on a surface, comprising: a generally planarprimary wheel that is rotatable about a central axis, said primary wheelcomprising a single planar member, said planar member having six stubaxles at fixed locations extending perpendicularly outwardly from oneside thereof, said locations being angularly equidistant apart andequidistant as well from the central axis; six secondary wheels, onewheel mounted on each stub axle, said secondary wheels being of equalwidth and diameter and configured as a generally cylindrical disk havinga diameter greater than the distance between angularly adjacent stubaxles; and three spacer means mounted on alternate stub axles adjacentsaid planar member, the length of said spacer means being greater thanis the width of a secondary wheel, said axles and wheels arranged suchthat at least two angularly adjacent wheels are in rolling contact withsaid surface at any one time, each of said secondary wheels arranged tofreely rotate independently of any other secondary wheel, andindependently as well of said primary wheel, said wheels positionedalong their respective axles in a manner causing each wheel of anangularly adjacent pair of wheels that is in contact with said surfaceto roll along a separate and parallel track.
 11. The wheel assemblyaccording to claim 10 wherein said spacer means comprises a cylindricalelement having an axial bore sized to fit over said stub axle, andwherein the height of said cylindrical element is greater than is thewidth of a secondary wheel.
 12. The wheel assembly according to claim 10wherein said spacer means comprises a cylindrical boss projectingaxially from one side of the secondary wheel.